TurretBarrel.cs

using System;
using UnityEngine;

public class TurretBarrel : MonoBehaviour
{
    public GameObject Projectile;
    public float AttackRange = 25f; // Distance
    public float AttackDelay = 1f; // Time

    public bool IsAlive { get; set; }

    private GameObject _player;
    private float _attackTimer;

    public void Start()
    {
        _player = GameObject.Find("PlayerShip");
        if (_player == null)
            throw new InvalidOperationException("Player was not found by TurretBarrel");

        _attackTimer = 0;
        IsAlive = false;
    }

    public void Update()
    {
        if (!IsAlive)
            return;

        if (CanFire())
            Fire();
        else
        {
            _attackTimer -= Time.deltaTime;
        }
    }

    private bool CanFire()
    {
        // Within range of player?
        return Vector3.Distance(_player.transform.position, transform.position) <= AttackRange && _attackTimer <= 0f;
    }

    private void Fire()
    {
        // Notes about the static Instantiate method:
        // System.Object is the same as Object
        // UnityEngine.Object is NOT the same

        _attackTimer = AttackDelay;
        var prefab = (GameObject)Instantiate(Projectile, transform.position, transform.rotation); // Instantiate is the same as GameObject.Instantiate
        prefab.transform.localScale = transform.localScale;
    }
}